Changeset db1d9d5 in sasmodels for sasmodels/models/flexible_cylinder.py
- Timestamp:
- Mar 28, 2019 3:16:51 PM (5 years ago)
- Branches:
- master, ticket-1257-vesicle-product, ticket_1156, ticket_822_more_unit_tests
- Children:
- 8795b6f
- Parents:
- a34b811
- File:
-
- 1 edited
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sasmodels/models/flexible_cylinder.py
r0507e09 rdb1d9d5 30 30 The Kuhn length $(b = 2*l_p)$ is also used to describe the stiffness of a chain. 31 31 32 The returned value is in units of $cm^{-1}$, on absolute scale.33 34 32 In the parameters, the sld and sld\_solvent represent the SLD of the cylinder 35 33 and solvent respectively. 36 34 37 Our model uses the form factor calculations implemented in a c-library provided 38 by the NIST Center for Neutron Research (Kline, 2006). 39 40 41 From the reference: 35 Our model uses the form factor calculations in reference [1] as implemented in a 36 c-library provided by the NIST Center for Neutron Research (Kline, 2006). This states: 42 37 43 38 'Method 3 With Excluded Volume' is used. … … 46 41 pseudocontinuous limit. 47 42 See equations (13,26-27) in the original reference for the details. 43 44 .. note:: 45 46 There are several typos in the original reference that have been corrected 47 by WRC [2]. Details of the corrections are in the reference below. Most notably 48 49 - Equation (13): the term $(1 - w(QR))$ should swap position with $w(QR)$ 50 51 - Equations (23) and (24) are incorrect; WRC has entered these into 52 Mathematica and solved analytically. The results were then converted to 53 code. 54 55 - Equation (27) should be $q0 = max(a3/(Rg^2)^{1/2},3)$ instead of 56 $max(a3*b(Rg^2)^{1/2},3)$ 57 58 - The scattering function is negative for a range of parameter values and 59 q-values that are experimentally accessible. A correction function has been 60 added to give the proper behavior. 61 62 63 **This is a model with complex behaviour depending on the ratio of** $L/b$ **and the 64 reader is strongly encouraged to read reference [1] before use.** 48 65 49 66 References … … 63 80 `flexible_cylinder.c <https://github.com/SasView/sasmodels/blob/master/sasmodels/models/flexible_cylinder.c>`_ 64 81 82 `wrc_cyl.c <https://github.com/SasView/sasmodels/blob/master/sasmodels/models/lib/wrc_cyl.c>`_ 83 65 84 Authorship and Verification 66 85 ---------------------------- 67 86 68 * **Author:** 69 * **Last Modified by:** 70 * **Last Reviewed by:** 87 * **Author:** 88 * **Last Modified by:** 89 * **Last Reviewed by:** Steve King **Date:** March 26, 2019 71 90 * **Source added by :** Steve King **Date:** March 25, 2019 72 91 """ … … 76 95 77 96 name = "flexible_cylinder" 78 title = "Flexible cylinder where the form factor is normalized by the volume " \97 title = "Flexible cylinder where the form factor is normalized by the volume " \ 79 98 "of the cylinder." 80 99 description = """Note : scale and contrast = (sld - sld_solvent) are both
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